The invention relates to a burner for use in the partial combustion of carbonaceous fuels, and particularly for the partial combustion of finely divided solid fuel, such as pulverized coal, in which the fuel is introduced together with an oxygen-containing gas and, optionally, a temperature moderator gas, into a reactor space.
Partial combustion, also known as gasification, of a fluid or solid carbonaceous fuel is obtained by the reaction of the fuel with oxygen. The fuel contains as useful components mainly carbon and hydrogen, which react with the supplied oxygen- and possibly with steam and carbon dioxide to form carbon monoxide and hydrogen. Depending on the temperature, the formation of methane is also possible. While the invention is described primarily with reference to pulverized coal, the burner according to the invention is also suitable for other carbonaceous fluid or finely divided solid fuels which can be partially combusted, such as gaseous or liquid hydrocarbons, lignite, pulverized wood, bitumen, soot and petroleum coke. In the gasification process the oxygen-containing gas may be pure oxygen or a gas containing molecular oxygen such as air; a mixture of air and oxygen can be used.
There are in principle two different processes for the partial combustion of e.g. solid fuel. In the first process, solid fuel in particulate form is contacted with an oxygen-containing gas in a reactor in a fixed or fluidized bed at a temperature below about 1000.degree. C. A draw back of this method is that not all types of solid fuel can be partially combusted in this manner. For example, high swelling coal is unsuitable since particles of such coal type easily sinter with the risk of clogging of the reactor.
A more advantageous process passes the fluid or finely divided fuel into a reactor at relatively high velocity. In the reactor a flame is maintained in which the fuel reacts with oxygen-containing gas at temperatures above 1000.degree. C. The carbonaceous fuel is usually passed directly or in a carrier fluid to the reactor via a burner, while the oxygen-containing gas is also passed via the burner to the reactor. In some processes a moderator gas such as steam or carbon dioxide is also passed via the burner to the reactor; such moderator gas is often advantageous for preventing premature contact of oxygen with the reactor gas, which might result in undesirable complete conversion of the reactor gas. A number of carbonaceous fuel burner designs are known, including U.S. Pat. No. 3,847,564; U.S. Pat. No. 3,945,942; U.S. Pat. No. 4,350,103; U.S. Pat. No. 4,351,647; U.S. Pat. No. 4,443,228; U.S. Pat. No. 4,458,607; U.S. Pat. No. 4,510,874; U.S. Pat. No. 4,519,321; and U.S. Pat. No. 4,523,529, all incorporated by reference.
A primary concern of such burners is to prevent damage to the burner front, also referred to as the burner face, caused by the heat load during the gasification process. To protect the burner front from overheating it is conventional to provide a refractory lining applied to the outer surface of the burner front wall for resisting the heat load during operation of the burner and/or provide the burner front a hollow wall member with internal cooling passages through which cooling fluid is circulated at a rapid rate. A drawback of the latter approach is that fabrication is difficult because very substantial amounts of heat must be transferred from the front face to the cooling fluid in a small volume with limited accessability.